The present invention relates, in general, to a device and method for recognition of a position of a load on a lifting gear.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
In general a lifting gear is used to lift a load, using ropes or cables. The load may hereby be attached to a load-carrying member, e.g. spreader. In the following description, a reference to “load” generally implies a reference to the load itself or also to the load-carrying member which carries the load.
German patent publication no. DE 198 36 103 A1 describes a crane which includes a trolley for horizontal and/or vertical movement of a load. Mounted to the trolley are several LED spotlights and a camera which can be oriented in the direction of the load. An optical marker is applied on the load and is recorded by the camera.
FIG. 4 shows a schematic illustration of a prior art position recognition device, using a camera C mounted to a trolley T, whereby an active light source LS is associated with the camera C. The light source LS is a spotlight which illuminates a reflector R. The reflector R reflects light, e.g. an infrared beam, back to the camera C. Thus, light has to travel back and forth, i.e. twice the distance between the camera C and the reflector R. The image captured by the camera C is then fed to an image processing system for determining a position or a swinging motion of the load. However, the intensity of incident light in the camera C is slight as a result of the two-way travel of light.
It would be desirable and advantageous to provide an improved method and device for recognition of a position of a load on a lifting gear to obviate prior art shortcomings and to withstand potential adverse environmental effects.